Quantitating excess tissue sodium

Using changes in tissue [Na⁺] concentration alone as done with Na⁺ MRI may not accurately quantitate excess tissue Na⁺, particularly in cellular tissues. However, individually quantitating alterations in tissue Na⁺ and water content as possible with ashing studies may still accurately quantitate excess tissue Na⁺ in these situations. Furthermore, when tissue [Na⁺] exceeds plasma [Na⁺], excess tissue Na⁺ must be present.